The impact of toroidal mode coupling on high-density discharges in J-TEXT
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Peng Deng,
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Wenzhe Mao,
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Zhipeng Chen,
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Yinan Zhou,
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Peng Shi,
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Zhoujun Yang,
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Li Gao,
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Tao Lan,
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Jinlin Xie,
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Hong Li,
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Zian Wei,
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Adi Liu,
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Chu Zhou,
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Weixing Ding,
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Wandong Liu,
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Ge Zhuang
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Abstract
Density limit has long been a widely studied issue influencing the operating range of tokamaks. The rapid growth of the m/n = 2/1 (where m and n are poloidal and toroidal mode numbers, respectively) tearing mode is generally regarded as a primary precursor to the density limit disruption. In this experiment, the coupling of the m/n=1/1 mode and the m/n = 2/1 mode in high density plasma was observed. During a sawtooth cycle, the frequencies of the two modes gradually converge until they become equal. After that, toroidal coupling occurs between the 1/1 and 2/1 modes, resulting in a mutually fixed phase relationship. With the occurrence of toroidal coupling, the 2/1 mode will be stabilized. Prior to the disruption, the cessation of the 1/1 and 2/1 mode coupling, along with the rapid growth in the amplitude of the 2/1 mode, can be observed. Additionally, under the same parameters, comparing discharges with or without the 1/1 mode, it is found that the presence of the 1/1 mode leads to higher plasma density and temperature parameters.
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